T&T: Tachometer Problem

[Ken Bloomfield]

On my Marine Trader 50', the old tachs running off the Perkins engine 
alternator field (also have parallel Aetna Engineering with magnetic senders 
on the engine) do exactly what was reported, that is periodically fall to 
zero and then bingo resume for a while, then zero etc.

The diagnosis of the battery charge is exactly correct, and the solution 
mentioned regarding giving the battery a load is also correct.  My inverter 
suffices as a load.  Also, if while you are running you have your generator 
on providing 120 VAC to the boat, be sure your charger is not also poking 
amps into the batteries, as this will ensure that there is no need for the 
engine alternators to provide current and thus ensure the bouncing tachs.  I 
really don't care as the old tachs are terrible in terms of calibration on 
my boat, and the PO had installed the Aetna Engineering tachs which are dead 
accurate and I love them.  I pay no attention to the old tachs, and leave 
them in only to continue the engine hour totalization.

All the best,
Ken

Ken Bloomfield
Cell# 865-293-2174
MTOA# 2062
AGLCA# 3529
M/V Tellico Lady, 50' Marine Trader-Walkaround
Maryville, TN